Lesser Tengu are usually depicted as anthropomorphic (usually crows or birds of prey like kites), with a diet consisting of any type of meat (not picky with source). Usually wear yamabushi robes, may carry weapons or other items (usually stolen from humans).
Unlike Touhou’s representation of Tengu, which operates as a fully-functional society, their folkloric origins tend to behave a lot more like wild birds. Occasionally they work together or with other youkai, but for the most part, they are solitary creatures. Like the birds they’re represented to be, they tend to collect things that are valuable - whether they be mere trinkets or true magical items. If you’re clever, these items can be traded for.
This type of tengu is noticeable for having very little respect for humans - often committing acts we’d deem as atrocities for fun, and take a higher level of joy in tormenting places of religious worship and those who work in them. When angered, they can be quite destructive. Though, given their rather vicious natures, there’s quite a few stories which involve outsmarting them for the valuable items they possess.
They are the original form which the Tengu take in their lore.
Note: There is a variant of Kotengu known as ‘Guhin’, where instead of having a bird’s beak, they have a canine snout instead. There are no other differences between these two types of Tengu, other than that Guhin are noticeably protective of their territories.
Also, there are two further types: Kawa tengu, and Shiba tengu, which are both known to be riverdwelling, and at least in the Shiba’s variant, quite possibly properly considered types of kappa.